title: Matrix-free high-resolution imaging mass spectrometry with high-energy ion projectiles.
abstract: The importance of imaging mass spectrometry (MS) for visualizing the spatial distribution of molecular species in biological tissues and cells is growing. We have developed a new system for imaging MS using MeV ion beams, termed MeV-secondary ion mass spectrometry (MeV-SIMS) here, and demonstrated more than 1000-fold increase in molecular ion yield from a peptide sample (1154 Da), compared to keV ion irradiation. This significant enhancement of the molecular ion yield is attributed to electronic excitation induced in the near-surface region by the impact of high energy ions. In addition, the secondary ion efficiency for biologically important compounds (>1 kDa) increased to more than 10(10) cm(-2), demonstrating that the current technique could, in principle, achieve micrometer lateral resolution. In addition to MeV-SIMS, peptide compounds were also analyzed with cluster-SIMS and the results indicated that in the former method the molecular ion yields increased substantially compared to the latter. To assess the capability of MeV-SIMS to acquire heavy-ion images, we have prepared a micropatterned peptide surface and successfully obtained mass spectrometric imaging of the deprotonated peptides (m/z 1153) without any matrix enhancement. The results obtained in this study indicate that the MeV-SIMS technique can be a powerful tool for high-resolution imaging in the mass range from 100 to over 1000 Da.
authors.affiliation: Department of Nuclear Engineering, Kyoto University, Sakyo, Kyoto, 606-8501, Japan. yukai@nucleng.kyoto-u.ac.jp
authors.forename: Yoshihiko
authors.initials: Y
authors.lastname: Nakata
authors.forename: Yoshiro
authors.initials: Y
authors.lastname: Honda
authors.forename: Satoshi
authors.initials: S
authors.lastname: Ninomiya
authors.forename: Toshio
authors.initials: T
authors.lastname: Seki
authors.forename: Takaaki
authors.initials: T
authors.lastname: Aoki
authors.forename: Jiro
authors.initials: J
authors.lastname: Matsuo
mesh_terms: D003952:Diagnostic Imaging / Q000295:instrumentation* / Q000379:methods*; D007091:Image Processing, Computer-Assisted / Q000379:methods; D007477:Ions / Q000737:chemistry; D013058:Mass Spectrometry / Q000295:instrumentation* / Q000379:methods*; D008970:Molecular Weight; D010455:Peptides / Q000737:chemistry*; D012680:Sensitivity and Specificity
chemical_list: D007477:Ions; D010455:Peptides